Debugging the Scheduler in Oracle 11g Databases

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Unix—all releases

Something that has not been made very clear in the Oracle Scheduler documentation is that redirection cannot be used in jobs (<, >, >>, |, &&, ||). Therefore, many developers have tried to use it. So, let’s keep in mind that we cannot use redirection, not in 11g as well as older releases of the database.

The scripts must be executable, so don’t forget to set the execution bits. This might seem like knocking down an open door, but it’s easily forgotten.

The user (who is the process owner of the external job and is nobody:nobody by default) should be able to execute the $ORACLE_HOME/bin/extjob file. In Unix, this means that the user should have execution permissions on all the parent directories of this file. This is not something specific to Oracle; it’s just the way a Unix file system works. Really! Check it out. Since 10gR1, Oracle does not give execution privileges to others. A simple test for this is to try starting SQL*Plus as a user who is neither the Oracle installation user, nor a member of the DBA group—but a regular user. If you get all kinds of errors, then it implies that the permissions are not correct, assuming that the environment variables (ORACLE_HOME and PATH) are set up correctly.

The $ORACLE_HOME/install/changePerm.sh script can fix the permissions within ORACLE_HOME (for 10g). In Oracle 11g, this again changed and is no longer needed. The Scheduler interprets the return code of external jobs and records it in the *_scheduler_job_run_details view. This interpretation can be very misleading, especially when using your own exit codes. For example, when you code your script to check the number of arguments, and code an exit 1 when you find the incorrect number of arguments, the error number is translated to ORA-27301: OS failure message:No such file or directory by Oracle using the code in errno.h. In 11g, the Scheduler also records the return code in the error# column. This lets us recognize the error code better and find where it is raised in the script that ran, when the error codes are unique within the script.

When Oracle started with Scheduler, there were some quick changes. Here are the most important changes listed that could cause us problems when the definitions of the mentioned files are not exactly as listed:

  • 10.2.0.1: $ORACLE_HOME/bin/extjob should be owned by the user who runs the jobs (process owner) and have 6550 permissions (setuid process owner). In a regular notation, that is what ls –l shows, and the privileges should be -r-sr-s—.
  • 10.2.0.2: $ORACLE_HOME/rdbms/admin/externaljob.ora should be owned by root. This file is owned by the Oracle user (the user who installed Oracle) and the Oracle install group with 644 permissions or -rw-r—-r–, as shown by ls –l. This file controls which operating system user is going to be the process owner, or which user is going to run the job. The default contents of this file are as shown in the following screenshot:

Debugging the Scheduler in Oracle 11g Databases

$ORACLE_HOME/bin/extjob must be the setuid root (permissions 4750 or -rwsr-x—) and executable for the Oracle install group, where the setuid root means that the root should be the owner of the file. This also means that while executing this binary, we temporarily get root privileges on the system.

$ ORACLE_HOME/bin/extjobo should have normal 755 or -rwxr-xr-x permissions,and be owned by the normal Oracle software owner and group. If this file is missing, just copy it from $ORACLE_HOME/bin/extjob.

On AIX, this is the first release that has external job support.

  • 11g release: I n 11g, the same files as in 10.2.0.2 exist with the same permissions. But $ORACLE_HOME/bin/jssu is owned by root and the Oracle install group with the setuid root (permissions 4750 or -rwsr-x—).

It is undoubtedly best to stop using the old 10g external jobs and migrate to the 11g external jobs with credentials as soon as possible.

The security of the remote external jobs is better because of the use of credentials instead of falling back to the contents of a single file in $ORACLE_HOME/, and the flexibility is much better. In 11g, the process owner of the remote external jobs is controlled by the credential and not by a file.

Windows usage

On Windows, this is a little easier with regard to file system security. The OracleJobscheduler service must exist in a running state, and the user who runs this service should have the Logon as batch job privilege. A .batfile cannot be run directly, but should be called as an argument of cmd.exe, for example:

--/
BEGIN
DBMS_SCHEDULER.create_job
(
job_name => 'env_windows',
job_type => 'EXECUTABLE',
number_of_arguments => 2,
job_action => 'C:windowssystem32cmd.exe',
auto_drop => FALSE,
enabled => FALSE
);
DBMS_SCHEDULER.set_job_argument_value('env_windows',1,'/c');
DBMS_SCHEDULER.set_job_argument_value('env_windows',2,
'd:temptest.bat');
end;
/

This job named env_windows calls cmd.exe, which eventually runs the script named test.bat that we created in d:temp. When the script we want to call needs arguments, they should be listed from argument number 3 onwards.

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